The designs of newer generations of gas turbine engines strive to reach increasingly stringent goals of emissions reduction. Whether the product of internal goals or environmental regulations, engine makers are working to deliver engines with ultra-low emissions, and which produce low levels of various combustion by-products. However, these new designs are prone to producing thermo-acoustic instabilities, sometimes referred to as “combustion instabilities”. Combustion instabilities cause engines to produce high levels of noise, which can be discomforting for passengers, and in some cases can lead to engine durability issues.
The root causes of combustion instabilities are challenging to understand, as combustion instabilities can be the product of fuel-flow perturbations, flame thermodynamics, acoustic couplings between a combustor of the engine and various pipes and bleed ports, as well as other factors. Traditional attempts to address combustion instabilities centre around modifications to the structure of the engine or the use of various noise-mitigating add-on devices. Both of these techniques increase the weight and the complexity of the engine.
As such, there is room for improvement.